Joliet weather in September: Joliet, Illinois: normal highs, lows, rain and records for September
Joliet in September has a normal high of 76°F and a normal low of 55°F, a daily mean of 66°F, falling from 80°F on the 1st to 71°F by the 30th. Measurable precipitation falls on 8 days in a normal September, 3.17 inches in all. (NOAA 1991-2020 normals)
In metric: a normal high of 25°C and low of 13°C, 81 mm of precipitation in September.
- NOAA stationJoliet Brandon Rd Dam
- Station IDUSC00114530
- Location41.50°N 88.10°W
- Elevation543 ft (166 m)
- Population151,837
- Jan 31° 17°
- Feb 35° 20°
- Mar 47° 29°
- Apr 60° 39°
- May 71° 49°
- Jun 80° 60°
- Jul 84° 64°
- Aug 82° 63°
- Sep 76° 55°
- Oct 63° 43°
- Nov 49° 32°
- Dec 36° 22°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
How warm is Joliet in September?
The normal high is 76°F and the normal low 55°F, for a daily mean of 65.7°F. September is 6.6°F cooler than August and 12.4°F warmer than October. September is the 4th warmest month of the year in Joliet and the 6th wettest. Across the month the normal high falls 9°F, from 80°F on September 1 to 71°F on September 30. From one year to the next September's mean temperature typically moves about 2.6°F either way (NOAA's standard deviation), so roughly two Septembers in three average between 63°F and 68°F.
Bars above: each day's normal high to low. Columns below: the chance of 0.01 inch or more of precipitation that day, on a scale of 0 to 100% (highest 29%).
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in |
|---|---|---|---|---|
| September 1 | 80°F | 61°F | 28% | 19% |
| September 8 | 79°F | 58°F | 27% | 18% |
| September 15 | 77°F | 56°F | 27% | 17% |
| September 22 | 74°F | 53°F | 28% | 17% |
| September 30 | 71°F | 49°F | 29% | 16% |
Every day of September: normal high, low and chance of precipitation (warmest afternoon September 1, coldest night September 30)
| Day | High | Low | Chance of 0.01 in | Chance of 0.10 in | Daylight |
|---|---|---|---|---|---|
| September 1 | 80°F | 61°F | 28% | 19% | 13 h 10 min |
| September 2 | 80°F | 60°F | 27% | 19% | 13 h 10 min |
| September 3 | 80°F | 60°F | 27% | 18% | 13 h 10 min |
| September 4 | 80°F | 60°F | 27% | 18% | 13 h |
| September 5 | 79°F | 59°F | 27% | 18% | 13 h |
| September 6 | 79°F | 59°F | 27% | 18% | 13 h |
| September 7 | 79°F | 59°F | 27% | 18% | 12 h 50 min |
| September 8 | 79°F | 58°F | 27% | 18% | 12 h 50 min |
| September 9 | 79°F | 58°F | 27% | 18% | 12 h 50 min |
| September 10 | 78°F | 58°F | 27% | 18% | 12 h 50 min |
| September 11 | 78°F | 57°F | 27% | 18% | 12 h 40 min |
| September 12 | 78°F | 57°F | 27% | 18% | 12 h 40 min |
| September 13 | 77°F | 57°F | 27% | 18% | 12 h 40 min |
| September 14 | 77°F | 56°F | 27% | 17% | 12 h 40 min |
| September 15 | 77°F | 56°F | 27% | 17% | 12 h 30 min |
| September 16 | 76°F | 55°F | 27% | 17% | 12 h 30 min |
| September 17 | 76°F | 55°F | 27% | 17% | 12 h 30 min |
| September 18 | 76°F | 54°F | 27% | 17% | 12 h 20 min |
| September 19 | 75°F | 54°F | 27% | 17% | 12 h 20 min |
| September 20 | 75°F | 54°F | 28% | 17% | 12 h 20 min |
| September 21 | 75°F | 53°F | 28% | 17% | 12 h 20 min |
| September 22 | 74°F | 53°F | 28% | 17% | 12 h 10 min |
| September 23 | 74°F | 52°F | 28% | 17% | 12 h 10 min |
| September 24 | 73°F | 52°F | 28% | 17% | 12 h 10 min |
| September 25 | 73°F | 51°F | 28% | 17% | 12 h 10 min |
| September 26 | 73°F | 51°F | 28% | 17% | 12 h |
| September 27 | 72°F | 51°F | 28% | 16% | 12 h |
| September 28 | 72°F | 50°F | 28% | 16% | 12 h |
| September 29 | 71°F | 50°F | 29% | 16% | 11 h 50 min |
| September 30 | 71°F | 49°F | 29% | 16% | 11 h 50 min |
- Normal high
- 76°FSeptember average
- Normal low
- 55°FSeptember average
- Precipitation
- 3.17 inmonth total
- Days with precipitation
- 80.01 inch or more
- Days at 90°F or more
- 2
- Daylight
- 13 h 10 min to 11 h 50 minSeptember 1 to September 30
- Days at 70°F or more
- 23
- Days at 80°F or more
- 12
- Sunshine
- 80%of clear-sky sunlight (NASA)
Source: NOAA NCEI 1991-2020 daily normals, station USC00114530; monthly normals. Daylight is computed from the place's latitude with NOAA's solar equations.
Does it rain in Joliet in September?
On a given September day the chance of 0.01 inch or more is 28% on average, highest around September 30 (29%). In all, 3.17 in falls on 8 days of a normal September, 1 of them with an inch or more.
In a normal September in Joliet, 2 days reach 90°F.
Source: NOAA NCEI 1991-2020 daily and monthly normals, station USC00114530.
What are the records for September in Joliet?
The warmest September temperature on this station's record (since 1975) is 97°F, on September 9, 1978; the coldest is 32°F, on September 24, 1983. The wettest September brought 13.20 in (1961).
The September mean against the 1991-2020 normal of 65.7°F: 2022 65.6°F (−0.1), 2023 66.4°F (+0.7), 2024 68.0°F (+2.3), 2025 68.0°F (+2.3), 2026 69.9°F (+4.2). 4 of 5 ran warmer than normal.
| September | Mean | Against normal | Precip. |
|---|---|---|---|
| 2022 | 65.6°F | −0.1°F | 1.87 in |
| 2023 | 66.4°F | +0.7°F | 6.76 in |
| 2024 | 68.0°F | +2.3°F | 1.90 in |
| 2025 | 68.0°F | +2.3°F | 0.94 in |
| 2026 | 69.9°F | +4.2°F | 4.49 in |
Source: records: ACIS, station USC00114530; recent months: ACIS, station USC00114530. Records and recent months use complete months only.
How does September in Joliet compare across Illinois?
Across the 144 places PlainClimate covers in Illinois, September normal highs run from 72°F in Barrington to 84°F in Anna; Joliet's is 76°F.
Source: NOAA NCEI 1991-2020 monthly normals for every station in the state.